Let's put it this way, the legacy of this season will be:
3 okay exotic weapons that are kinda fun but not remotely top-tier;
1 static god-rolled energy shotgun that will dominate the crucible more than Mindbender's Ambition did, which was obtained via the most aggravating and broken community quest ever*;
6 actual new legendary weapons, only two of which I would consider interesting and even that is strictly PvE, because it's tied to;
Some armor mods that do neat stuff with those 6 weapons on PvE kills, but whose use was primarily enabled by a mod from the seasonal artifact that's going away;
9 random-rolled reprises of year 1 weapons, only 3 of which see any use at all;
6 weapons from Trials of Osiris, one of which could be the Kinetic version of the shotgun mentioned above, two others that are nice but overshadowed by other options, all obtained by running your dick through a meatgrinder that even streamers gave up on;
Loss of the playerbase's trust that Bungie can produce engaging content going forward.
*A lot of the season was focused on a limited-time new public event whose rewards ceased being meaningful after the first month-ish, which received a little-noticed (because almost no one was still doing them) boost in difficulty partway through the season. The upgraded-difficulty version probably wanted 6+ people per instance, but the way instance matchmaking works the only way to get more than 5 requires laborious out-of-game party coordination to have people join and leave instances until some of them show up together, then other party members have to join the ones who are already together, because only two people can slot into fireteams with one of the players already in the event. So trying to pull off the event with randoms is hard, especially if someone in the instance isn't doing the event, doesn't know what they're doing, etc. Then Bungie asked the playerbase to complete 3 MILLION events EACH on 3 locations. Now, each player participating in a successful event counted as a completion towards that 9 MILLION, but the events mostly failed and people were dropping out like crazy. After the first day, the quest step was only a few percent completed, with projections that it could take months to finish and speculation that Bungie meant the quest to be failed. So Bungie had to frantically patch things so that the events could be completed faster, the boss enemies that could effortlessly disrupt your progress got tuned down, and credit for completions was increased by 5x (and 10x on the weekend). So the quest step was finished within a week, and people were ready to be done with it. There was another step to get 1k shotgun kills, which could be ground out in a half-hour to an hour if you built for it properly and knew where to grind. Then there was a final step to claim your reward... except when you activated the step, it returned you to the initial spawn on the moon instead of the special quest zone. The quest was bugged and uncompleteable for 100% of the player base, and this somehow didn't get noticed during testing. So players had to wait for Bungie to issue another patch to finally get the shotgun, at which point they were more relieved it was over than excited about the gun.